Reduction of Pressure Gradient and Turbulence Using Vortex Generators in Prosthetic Heart Valves

Hatoum, Hoda; Dasi, Lakshmi Prasad

doi:10.1007/s10439-018-02128-6

Cited by 23 publications

(16 citation statements)

References 43 publications

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“…In reality, the reported echocardiographic mean gradient derived from the aortic valve velocity accounts only for, and attributes all increased velocity to, convective acceleration that is assumed to be from a reduced area. In addition to omitting the proximal LVOT pressure, Bernoulli omits other causes of increased velocity as nonconvective variables (flow acceleration and viscous forces), pressure recovery, flow amount, and type between different valves 30 , 31 , 32 (laminar versus turbulent, single versus multiple zones of flow convergence in series, and long versus short valve frames). An elevated aortic velocity attributable to the aforementioned factors, apart from a true transaortic gradient from a reduced area, is attributed by echocardiography as convective acceleration and thus leads to an unpredictable overestimation of the mean gradient.…”

Section: Discussionmentioning

confidence: 99%

Comparison of Transvalvular Aortic Mean Gradients Obtained by Intraprocedural Echocardiography and Invasive Measurement in Balloon and Self‐Expanding Transcatheter Valves

Abbas

Mando

Kadri

et al. 2021

JAHA

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Background Concerns about discordance between echocardiographic and invasive mean gradients after transcatheter aortic valve replacement (TAVR) with balloon‐expandable valves (BEVs) versus self‐expanding valves (SEVs) exist. Methods and Results In a multicenter study, direct‐invasive and echocardiography‐derived transvalvular mean gradients obtained before and after TAVR were compared as well as post‐TAVR and discharge echocardiographic mean gradients in BEVs versus SEVs in 808 patients. Pre‐TAVR, there was good correlation ( R =0.614; P <0.0001) between direct‐invasive and echocardiography‐derived mean gradients and weak correlation ( R =0.138; P <0.0001) post‐TAVR. Compared with post‐TAVR echocardiographic mean gradients, both valves exhibit lower invasive and higher discharge echocardiographic mean gradients. Despite similar invasive mean gradients, a small BEV exhibits higher post‐TAVR and discharge echocardiographic mean gradients than a large BEV, whereas small and large SEVs exhibit similar post‐TAVR and discharge mean gradients. An ejection fraction <50% ( P =0.028) and higher Society of Thoracic Surgeons predicted risk of mortality score ( P =0.007), but not invasive or echocardiographic mean gradient ≥10 mm Hg ( P =0.378 and P =0.341, respectively), nor discharge echocardiographic mean gradient ≥20 mm Hg ( P =0.393), were associated with increased 2‐year mortality. Conclusions Invasively measured and echocardiography‐derived transvalvular mean gradients correlate well in aortic stenosis but weakly post‐TAVR. Post‐TAVR, echocardiography overestimates transvalvular mean gradients compared with invasive measurements, and poor correlation suggests these modalities cannot be used interchangeably. Moreover, echocardiographic mean gradients are higher on discharge than post‐TAVR in all valves. Despite similar invasive mean gradients, a small BEV exhibits higher post‐TAVR and discharge echocardiographic mean gradients than a large BEV, whereas small and large SEVs exhibit similar post‐TAVR and discharge mean gradients. Immediately post‐TAVR, elevated echocardiographic‐derived mean gradients should be assessed with caution and compared with direct‐invasive mean gradients. A low ejection fraction and higher Society of Thoracic Surgeons score, but not elevated mean gradients, are associated with increased 2‐year mortality.

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Section: Discussionmentioning

confidence: 99%

Comparison of Transvalvular Aortic Mean Gradients Obtained by Intraprocedural Echocardiography and Invasive Measurement in Balloon and Self‐Expanding Transcatheter Valves

Abbas

Mando

Kadri

et al. 2021

JAHA

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“…The sinus radius of the aortic valve chamber is 19 mm, sinus height 21.6 mm, and aortic radius 12.7 mm. The chamber was set up into the aortic position of a left heart pulse duplicator flow loop as previously described in other publications [7,14,[27][28][29][30]. Sinus hemodynamics were assessed for each of the three leaflets through positioning the valve in all 3 possible positions in the aortic root model keeping the commissures aligned with those of the representative native model.…”

Section: Hemodynamic Assessmentmentioning

confidence: 99%

Spatiotemporal Complexity of the Aortic Sinus Vortex as a Function of Leaflet Calcification

Hatoum

Dasi

2019

Ann Biomed Eng

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Several studies have shown the variation of aortic sinus structures' hemodynamics with different flow and geometric characteristics. They have also correlated aortic sinus hemodynamics with the progression and evolution of calcific aortic valve disease (CAVD). This study aims at visualizing aortic sinus fluid structure variations as functions of different leaflet calcification degrees and assessing their potential relationship with CAVD. A degenerated 23mm Carpentier-Edwards Perimount Magna valve extracted from a redo-surgery patient was implanted in an aortic root model and tested in a pulse duplicator left heart simulator. The valve has 3 leaflets with 3 different levels of calcium distribution: mild, moderate and severe. High-speed imaging and particle image velocimetry were performed to assess sinus vortices, leaflet tip position and velocity along with shear stress. Results have shown that (a) aortic sinus vortices initiation, entrapment and evolution varied with different calcified leaflet exposure; (b) higher velocities in the sinus were calculated with the mildly calcified leaflet compared to the moderately and severely calcified ones; (c) during systole, the mildly calcified leaflet sinus case shows the most spread-out and higher ranges of shear stress probabilities and highest magnitudes going from (−1.5 to +1.8 Pa) compared with (−1.0 to +1.0Pa) for moderately and severely calcified leaflets. The higher the calcification degree the lower the shear stress range and likelihoods of having higher shear stress. This holds in diastole as well. This study shows the impact of calcification on the aortic sinus flow structures.

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“…With the objective of minimising the risk for platelet activation and haemolysis, previous studies utilised passive control flow surfaces such as VGs (Murphy et al. 2010; Hatoum & Dasi 2019). Hatoum & Dasi (2019) documented through in-vitro experiments that the use of VGs allows one to mitigate turbulent stresses and reduce the transvalvular pressure drop.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of turbulent features past different mechanical aortic valves

2022

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Flow through mechanical aortic valves (MAVs) has been constantly associated to higher haemolysis and platelet activation levels with respect to native valves, due to non-physiologic haemodynamic features. Both computational and experimental investigations have correlated the blood damage to augmented levels of turbulent stress downstream of MAVs. This study provides a computational estimation, drawn from high-resolution direct numerical simulations, of turbulent and fluctuating viscous stresses in three different MAV configurations, at subsequent stages of the cardiac cycle. The configurations comprise a St. Judes Medical Regent valve (SJMV), a Lapeyre-Triflo FURTIVA valve (LTFV) with three leaflets, and a SJMV with vortex generators (VGs). Non-standard configurations are expected to mitigate the mean stress level on blood constituents reducing the turbulent production. Computations are carried out by means of a finite-difference flow solver with a direct-forcing immersed boundary technique to handle fixed and moving bodies. The VGs are found to provide instabilities which corrupt the Kármán-like vortex shedding downstream of the leaflets, reducing the intensity of turbulent kinetic energy at the peak flow rate, thus lowering the local Reynolds shear stress. Conversely, the LTFV configuration provides comparable haemodynamic performance at peak flow rate but further reduced stress level in the deceleration phase. These interpretations are supported by probability density distributions from three-dimensional fields, and further corroborated by a pointwise mapping of the Taylor length scale and local energy spectra. The outcomes of this study might potentially be exploited to improve the design of new-generation MAVs, with the aim of decreasing the risk of thromboembolic complications.

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Reduction of Pressure Gradient and Turbulence Using Vortex Generators in Prosthetic Heart Valves

Cited by 23 publications

References 43 publications

Comparison of Transvalvular Aortic Mean Gradients Obtained by Intraprocedural Echocardiography and Invasive Measurement in Balloon and Self‐Expanding Transcatheter Valves

Comparison of Transvalvular Aortic Mean Gradients Obtained by Intraprocedural Echocardiography and Invasive Measurement in Balloon and Self‐Expanding Transcatheter Valves

Spatiotemporal Complexity of the Aortic Sinus Vortex as a Function of Leaflet Calcification

Numerical investigation of turbulent features past different mechanical aortic valves

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